In spite of the widespread conviction, held by both pro- and anti-Israel activists, that AIPAC holds unmatched sway over American Middle East policy, the outfit's recent loss underscores the real and growing limits of its political power. It was only a matter of time before someone zeroed in on the organization's fundamental dilemma and made it choose between form (bipartisanship) and substance (pro-Israel legislation). Now that President Barack Obama has forced that choice, AIPAC is clearly at a crossroads.

For almost a decade now, AIPAC's biggest battle in Washington has been to prevent Iran from acquiring a nuclear weapons program. The sanctions provided for in the most recent bill were to come into effect only if negotiations over a permanent agreement to replace the interim agreement failed. Nonetheless, Obama threatened to veto the bill and the Democrats backed off. When Republicans wanted to push ahead, AIPAC chose bipartisanship over sanctions, siding with Democrats in asking to postpone the vote. "The better part of valor is to come back another day," said Amitay. "I'm sure it was a tough decision."

As Rosen explained, there was a collision between AIPAC's two core principles. "The problem of Iran is a cardinal issue, but bipartisanship is too," he said. It might be emotionally satisfying to act out when the vote goes against you, but AIPAC's main job is to produce bipartisan majorities. "AIPAC decided to pull a punch," Rosen went on, "because it had no other choice."

And that's precisely the problem--AIPAC had no choice. And now everyone sees it. The organization's power resides largely in the appearance of power, which depends on its presumed ability to punish those who act against it.

When AIPAC lost its campaign to stop the Carter Administration from selling F-15s to Saudi Arabia in 1978, the White House agreed not to equip the Saudi purchases with the most advanced equipment. But there were no concessions to sweeten the bitter taste of defeat this time around. AIPAC lets on that it's happy to have the bill on the legislative schedule for a vote sometime in the future. However, there will almost surely never be a vote on more sanctions while Obama sits in the Oval Office, because it is in the interest of both the administration and the Iranians to roll over the six-month interim agreement indefinitely--while Iran continues work on its ballistic missiles and warheads as well as "research and development" on its second-generation centrifuges. In other words, taken together with the fact that the administration intentionally collapsed the sanctions regime in order to empower the "moderate" Hassan Rouhani, the fight over Iran sanctions is over and AIPAC was routed.

AIPAC's failure is not simply the result of the fact that the lobbying group's preferred strategy of bipartisanship has been riddled with contradictions for almost half a century--even as it has kept wealthy Democratic donors on board. Rather, the group's bipartisan inclinations seem to have blinded them to the fact that the president had his own Middle East strategy--even as he mimed agreement with the general idea that Iran should be prevented from obtaining nuclear weapons.